Gonadotropes synthesize and secrete heterodimeric glycoproteins luteinizing hormone (LH) and follicle stimulating hormone (FSH) that are critical for reproductive function. The genes encoding the common alpha subunit (Cga) and the hormone-specific beta subunits (Lhb and Fshb) are coordinately regulated by hypothalamic gonadotropin-releasing hormone, steroids and gonadal peptides, inhibin and activin. Although a wealth of knowledge has accumulated on transcriptional control of gonadotropin beta subunits, post- transcriptional mechanisms of these genes are unknown. Recently, micro RNAs (miRNAs) produced by Dicer, an RNA endonuclease III, have emerged as key regulators of gene expression, mRNA stability and protein synthesis. Knowledge on miRNAs that regulate gonadotrope and consequently reproductive function is lacking. Our long-term research goal is to elucidate the in vivo mechanisms that regulate gonadotropin synthesis and secretion. The central hypothesis is that Dicer is a key factor in miRNA biogenesis in gonadotropes and plays essential roles in gonadotropin synthesis and consequently reproductive function. In Specific Aim 1, we will conditionally delete Dicer exclusively in gonadotropes by cre-lox technology and analyze gonadotropin synthesis and secretion. Additionally, we will use novel mouse strains, in which gonadotropes are labeled with GFP on a normal or activin receptor-II (Acvr2) null genetic background. Pure populations of gonadotropes will be isolated from these mice by cell sorting based on GFP fluorescence and miRNAs regulated by Acvr2 identified. In Specific Aim 2, reproductive phenotypes secondary to changes in gonadotropins as a result of Dicer deletion in gonadotropes will be determined. These studies should provide new knowledge on Dicer - dependent miRNAs in gonadotropes and identify novel post-transcriptional mechanisms for gonadotropin secretion. Delineation of mechanisms of gonadotropin secretion is fundamental to physiology of reproduction and offers long-term clinical benefits of diagnosing and treating gonadotropin-dependent fertility/infertility disorders.